Reduced radiated-noise rail

ABSTRACT

The invention relates to a profiled rail ( 1 ), especially for a railway track, with a reduced total radiated noise level when in use. In order to reduce the noise radiation level, at least one web side surface ( 31 ) is substantially concavely rounded without any salient points in the lower region ( 31′ ) between the transition edge ( 32 ) on the side of the rail patten ( 3 ) and the center of gravity axis (X) in the rail cross-section and/or the height (H) of the pattern is increased by comparison with a normally profiled rail having a corresponding total rail height A.

BACKGROUND OF THE INVENTION

The invention relates to a profiled rail, especially a railway rail,having a reduced total radiated noise level when in use, and comprisinga foot section with a bottom surface, a web section, and a head sectionwith a tread surface, and having a rail height and preferably also arail head width, and in particular a moment of inertia and a sectionmodulus about the axis of the center of gravity, correspondingsubstantially to those of standard, normally profiled rails having thesame load-bearing capacity.

Running rails are profiled, rolled steel bars which are used to buildtrackways, especially railroad tracks, on which loads can beeconomically transported. On these tracks, metallic wheels, madepreferably from steel or having a steel tire, run on the tread surfaceof a section of the rail referred to as the rail head. The foot of therail, which is located opposite to and joined to the head by means of aweb, is connected with its bottom surface to a base structure.

In the course of development of railway systems, functionally optimizedcross-sectional profiles of rails were appropriately standardized forvarious loads and applications. In Europe, a frequently used standardprofile for railroad rails bears the designation UIC 60; the rail weighsapprox. 60 kg/m and tight dimensional tolerances of, for example, ±0.6mm for the rail height and ±0.5 mm for the width of the rail head arespecified. Tight tolerances in the rail profile are important,especially for the purpose of building a geometrically accurate trackintended to permit the speed of trains to be increased without any lossin ride comfort and without any major dynamic loads occurring. In orderto reduce wear, rails having heads exhibiting increased hardness arealready being manufactured and used.

Despite the highest possible dimensional accuracy, a tread or runningsurface of the best quality, and smoothness of the rails, as railwaycars travel along the track, vibrations, and thus radiated noise, occur.This airborne noise can attain high intensity, especially at hightransportation speeds, and it can cause considerable environmentalpollution. It has been found that the travel noise generated by trainsis caused to a considerable extent by airborne noise radiated from thesurface of the rail.

Attempts have already been made by sound-insulating surface sections ofthe rail to reduce the intensity of the radiated noise.

Applying a coating of vibration-damping material, as proposed inDE-A-4225581 or AT-AS 652/90, is only partially successful in achievingthis goal; it is also expensive, prevents visual inspection of the railin the track and, especially if reinforced polymers are used, it canitself be a source of environmental pollution. In addition, there havebeen several proposals, e.g. in DE-OS 4411833, to use elastic componentsin the fastening elements to reduce the transmission of vibrations tothe base structure and thus to reduce the amount of airborne noiseradiated from this source.

All the devices and arrangements so far proposed to reduce the airbornenoise radiated from rails or track installations have in common thedisadvantage that they are not very effective, and/or are veryexpensive, and are aimed essentially at reducing the transmission ofvibrations from the rail.

SUMMARY OF THE INVENTION

It is therefore a purpose of the invention to reduce or shape thevibration of the rail, when it is travelled on by trains movingespecially at high transportation speeds, so that the total level ofradiated noise and the noise pollution of the environment are reduced. Aparticular goal of the invention is thus to reduce the vibrations of thebody or the rail itself, which vibrations are responsible for generatingthe airborne noise, and thereby, in a simple manner, to reduce theradiated noise and the environmental pollution.

Using a profiled rail of the kind mentioned at the beginning, this taskor goal is accomplished in that at least one lateral web surface, atleast in the lower area between the transition edge at the foot of therail, namely the edge formed at the transition from the foot into thelateral web surface, on the one hand, and the axis of the center ofgravity, on the other hand, is concavely rounded and substantially freeof any angularities in the cross section of the rail, and/or the heightof the rail foot is larger compared with that of a standard profiledrail.

It has surprisingly been discovered that, contrary to what is assumed byexperts in the field, it is not the web between the head and foot of therail, vibrating like a membrane, that creates most of the radiatednoise. Instead, the rail head and in particular the foot of the railexhibit high solid-borne noise levels and thus contribute greatly to thelevel of the total sound pressure, and they in turn are chieflyresponsible for the noise pollution of the environment. The reasons forthe increased wave-like vibration in the longitudinal direction, i.e.the springiness, as a function of the frequency, for example, of oneflange of a rail foot have not yet been scientifically fully explained.However, it is assumed that angularities in the surface profile ordiscontinuous changes in the thickness of the cross section may act asvibration nodes or theoretical clamping points causing or permittingincreased vibrations to occur in sections of the rail profile, forexample in a flange of the rail foot. In the manner according to theinvention, increasing the height of the foot of the rail and/or inparticular ensuring the transition, without angularities, from the footinto the lateral surface of the web brings about a change in thevibrations in the area of the rail foot; as a result, the amount ofairborne noise radiated by the surfaces of the rail foot into theenvironment and possibly to a base structure, which reflects thisradiated noise, is reduced.

A further reduction in the radiated noise is achieved when thecross-sectional profile is designed symmetrically to the height axis, asa result of which the tendency for local vibration nodes to form in theprofiled bar is further reduced.

If, as further advantageously provided, the lower part and the upperpart of the lateral surface of the rail web between the transition edgeat the foot of the rail and the transition edge at the head of the rail,namely the edge which is formed when the lateral surface of the railhead merges into the upper surface of the web, are designed so as to beconcavely rounded and substantially free of angularities in the crosssection of the rail, the formation of vibrations, especially in sectionsof the rail profile which as a result radiate airborne noise, is furtherreduced.

It may be further advantageous from the point of view of manufacturingor rolling the rail, as well as for the purpose of minimizing theweight, but especially also in order to reduce airborne noise emission,if in the cross section of the rail the lateral surface of the rail webis made up of a circularly and/or an elliptically shaped lower and upperpart and possesses preferably a straight middle or intermediate section,merging tangentially with the aforesaid parts, and through this middlesection passes the axis of the center of gravity. It may be favorable inthis case if the minimum thickness of the rail web is the same as orgreater than that of standard rails.

A particularly favorable embodiment, in which the rail possesses a highload-bearing capacity while at the same time radiating a low level ofairborne noise, is achieved if the distance between the axis of thecenter of gravity and the bottom surface at the foot of the rail has avalue between (0.5 and 0.38), preferably between (0.47 and 0.41) timesthe height (A) of the rail.

The vibration sensitivity of the outer sections of the flanks of therail foot can be largely eliminated or minimized in a simple way if thefoot is less wide and/or higher compared with the respective standardrail profile.

If, as advantageously provided, the hardness of the material in thehead, and in particular in the tread area of the rail according to theinvention, has been increased, as is known in the art, it is possible tosubstantially reduce the resulting increase in the noise radiated bystandard profiles if, in addition, the hardness of the material in thefoot and in particular in the central area of the rail, which isarranged substantially symmetrically to the axis of the rail andcontains the bottom surface, is also increased; in this way, aparticularly stable embodiment possessing ideal functional properties isobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention is explained in more detail based onmethods of implementation and test results schematically illustrated inthe drawings.

FIG. 1 is a cross section through a standard UIC 60 rail.

FIG. 2 is a cross section through a rail reinforced according to theinvention in the foot area.

FIG. 3 is the cross section through a rail having rounded lateral webfaces, free of angularities, at foot of the rail.

FIG. 4 is a rail cross section with fully rounded web surfaces.

FIG. 5 depicts the total level of solid-borne noise and the weights ofrails as a function of the cross-sectional shape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a cross-sectional view of a standard UIC 60 rail. The railhas an overall height A of 172 mm, a head height of 37.55 mm from thetread surface 41 to the edge 34 where the transition is made to alateral surface 31 of the web, and a foot width B of 150 mm. Thedistance S of the axis X of the center of gravity from the bottomsurface 21 at the foot 2 of the rail is 80.95 mm.

A standard UIC 60 rail of this type, having a weight or mass of 60.84kg/m, was caused to vibrate by applying excitation in the form ofimpulses laterally or eccentrically at the tread surface 41, transverseto the longitudinal orientation, in a vertical and horizontal direction,and the maximum total level of solid-borne noise as well as the radiatedsound power were determined. The values determined for a standard rail,as shown in FIG. 5, bar B, represent base values for the UIC 60 whichcan be compared with the values obtained from rails according to theinvention. FIG. 2 depicts a rail according to the invention having areinforced foot 2, or a larger foot thickness H, compared with astandard UIC 60 rail. As a result, while maintaining the same overallrail height A, the distance S between the axis (X) of the center ofgravity and the bottom surface 21 is reduced and, as is also apparentfrom FIG. 5, bar 1, the weight of the rail is slightly increased.Compared with a standard rail, given the same excitation, this designleads to a reduction in the maximum total level of solid-borne noise andto a significant drop in the total level of airborne noise, as is alsoevident from FIG. 5, bar 1.

FIG. 3 shows a rail profile according to the invention in which the foot2 has a height H corresponding to the standard UIC 60 profile, but inwhich the lower part 31′ of the lateral surface 31 of the rail web 3,between the transition edge 32 at the foot and the intersection with theaxis X of the center of gravity, has a symmetrical, circularly roundedconfiguration free of angularities. Compared with the standard rail,when the same pulsating excitation was applied, this embodiment wasfound to have a much reduced total level of solid-borne noise and atotal level of radiated sound power that was lower by approximately 1.05dB, as shown diagrammatically in FIG. 5, bar 2, while the mass of therail (see lower part of FIG. 5, bar 2) was only slightly increased.

FIG. 4 shows another rail profile according to the invention whichpossesses fully rounded fishing spaces, or lateral web surfaces 31 freeof angularities, extending from the transition edge 32 at the foot ofthe rail to the transition edge 34 at the head of the rail, and having aplane-parallel middle section of the web 3 in the area of the axis ofthe center of gravity, said section merging tangentially into saidsurfaces. A continuous thickening of the web 3 towards the head 4 andthe foot 5 of the rail increases the mass of the rail 1 per metre, as isevident from the lower part of FIG. 5, bar 3. As also shown by bar 3 inthe upper part of FIG. 5, the maximum total level of solid-borne noiseis reduced to a very small percentage compared with the standard UIC 60profile, and also the total level of radiated sound power is reduced byabout 3.0 dB.

Compared with other standard rail profiles, rails embodying thecharacteristics according to the invention also exhibited substantiallylower total levels of radiated sound power.

What is claimed is:
 1. A profiled rail having a reduced radiated noiselevel when in use comprising a foot section with a top surface, a websection with a lateral web surface, a head section with a tread surface,a rail height, and a moment of inertia and a section modulus about anaxis extending through the center of gravity of the rail whose valuescorrespond substantially to those of a standard profiled rail having thesame load-bearing capacity, the rail having a cross-sectional profileformed symmetrically to a height axis of the rail and a concavelyrounded lower lateral surface area extending from the top surface of thefoot section to an intersection between the lateral web surface and theaxis extending through the center of gravity, the concavely roundedlower lateral surface area being free of angularities in thecross-sectional profile of the rail.
 2. A profiled rail according toclaim 1 wherein the foot section of the rail has a height which isgreater than that of the standard profiled rail.
 3. A profiled railaccording to claim 1 including a concavely rounded upper lateral surfacearea between an edge of the head section formed at a transition of thehead section into the lateral web surface which is free of angularitiesin the cross-sectional profile of the rail.
 4. A profiled rail accordingto claim 1 wherein, in the cross-sectional profile of the rail, thelateral web surface is defined by a circularly and/or ellipticallyshaped lower area and a circularly and/or elliptically shaped upperarea.
 5. A profiled rail according to claim 1 wherein a distance betweenthe axis extending through the center of gravity and a bottom surface atthe foot section of the rail has a value between 0.5 and 0.38 times theheight of the rail.
 6. A profiled rail according to caim 1 wherein adistance between the axis extending through the center of gravity and abottom surface at the foot of the rail has a value between 0.47 and 0.41times the rail height.
 7. A profiled rail according to claim 1 whereinthe foot section of the rail has a width which is narrower and/or aheight which is greater than those of the standard profiled rail.
 8. Aprofiled rail according to claim 1 wherein a portion of the raildefining the tread surface is harder than the web section or the footsection.
 9. A profiled rail according to claim 1 wherein a portion ofthe rail including the foot section located essentially symmetrical to aheight axis of the rail and containing a bottom surface of the footsection is harder than the web section.
 10. A profiled rail according toclaim 1 wherein the concavely rounded lower lateral surface area istangent to the top surface of the foot section and to the lateral websection.
 11. A profile rail according to claim 10 wherein the concavelyrounded lower lateral surface is a circularly rounded surface.
 12. Aprofile rail according to claim 11 wherein the circularly roundedsurface has a radius which is greater than a width of the web section.13. A profile rail having a reduced radiated noise level when in usecomprising a head section with a tread surface, a foot section and a websection having a thickness and spaced-apart, lateral web surfaces andconnecting the head section and the foot section, the foot sectiondefining an upper surface on each side of the web section, and concavelyrounded lower lateral surface areas extending tangentially from therespective upper surfaces of the foot section to the respective lateralweb surfaces, being tangent to the lateral web surfaces where an axisextending through the center of gravity of the rail intersects thelateral web surfaces, and having a radius which is larger than thethickness of the web section.
 14. A profiled rail having a reducedradiated noise level when in use comprising a foot section with an uppersurface, a web section having a thickness and a lateral web surface, ahead section with a tread surface, and having a rail height, and amoment of inertia and a section modulus about an axis extending throughthe center of gravity of the rail which correspond substantially tothose of a standard profiled rail having the same load-bearing capacity,the rail having a cross-sectional profile formed symmetrically to aheight axis of the rail and a circularly concavely rounded lower lateralsurface area between the upper surface of the foot section and thelateral web surface which has a radius of curvature that is larger thanthe thickness of the web.
 15. An improved profiled rail having a loadcarrying capacity, a reduction in radiated noise caused by wave-likevibrations of the improved rail when in use as compared to the radiatednoise of a rail with substantially the same load carrying capacity andhaving a standardized shape and size, the improved rail comprising afoot section, a web section with a lateral web surface, and a headsection with a tread surface, and having a rail height, with a rail headwidth and a moment of inertia and a section modulus about an axisextending through the center of gravity whose values correspondsubstantially to those of a standard profiled rail having the same loadcarrying capacity, the rail having a cross-sectional profile formedsymmetrically to a height axis of the rail and a concavely rounded lowerfillet surface which extends from the foot section to the lateral websurface and which has a radius that is greater than a thickness of theweb, thereby reducing the radiated noise of the improved rail ascompared to the noise caused by longitudinal vibrations in the rail withthe standardized size and shape.
 16. An improvement to a standardprofiled rail for reducing noise generated by the rail, the standardrail having a standard profile, standardized dimensions, a given loadcarrying capacity, a rail head, a foot and a web interconnecting thehead and the foot, the noise resulting from wave-like vibrations of atleast one of the rail head and the foot in a longitudinal direction ofthe rail, the standard rail having a section modulus about an axis ofits center of gravity, a standard foot with an upwardly facing standardfoot surface that includes an angular transition spaced from a lateralend of the foot and dividing the upwardly facing standard foot surfaceinto substantially flat portions having different angles relative to abottom surface of the foot section, the improvement comprising aconcavely rounded lower lateral transition surface between adjacentsurfaces of the web and the foot which is free of angularities in thecross section of the rail and which extends beyond a circular line thatis tangent to the lateral web surface and the upwardly facing footsurface and has a radius which is equal to a thickness of the web,whereby wave-like vibrations in the longitudinal direction of the railare reduced as compared to the wave-like vibrations in the longitudinaldirection generated by the standard rail.
 17. An improvement to astandard profiled rail for reducing noise generated by the rail, thestandard rail having a standard profile, standardized dimensions, agiven load carrying capacity, a rail head, a foot and a web having athickness interconnecting the head and the foot, the noise resultingfrom wave-like vibrations of at least one of the rail head and the footin a longitudinal direction of the rail, the standard rail having asection modulus about an axis of its center of gravity, a standard footwith an upwardly facing standard foot surface that includes an angulartransition spaced from a lateral end of the foot and dividing theupwardly facing standard foot surface into substantially flat portionshaving different angles relative to a bottom surface of the footsection, the improvement comprising a circularly rounded lower lateraltransition surface between adjacent surfaces of the web and the footwhich is tangent to the lateral web surface and the upwardly facing footsurface and has a radius which is greater than a thickness of the web,whereby wave-like vibrations in the longitudinal direction of the railare reduced as compared to the wave-like vibrations in the longitudinaldirection generated by the standard rail.
 18. A method of reducinglongitudinal vibrations in a standard rail having a predetermined shapeand predetermined dimensions conforming to a preset standard, thestandard rail defining a head, a foot, a web having a thickness andconnecting the head and the foot, and a curved transition surfaceextending from the foot to the web, the method comprising the steps of:providing a modified rail by forming a continuous transition extendingfrom a lateral surface of the web to the foot which is free ofangularities and, in a cross-section of the rail, extends beyond acircular line having a radius equal to the thickness of the web andbeing tangent to the lateral surface and an adjacent surface of thefoot; installing the modified rail on a railway track; and rollingrailway vehicles over the modified rail of the railroad track; wherebyairborne noise generated by the modified rail when railway vehicles rollover it is reduced as compared to the airborne noise generated by thecorresponding standard rail.